For RF (Radio Frequency) applications in MEMS structures and devices the dielectric properties of the support structures are of great importance, and it is desirable to eliminate “cross-talk” between neighbouring components or elements on chips or wafers on which the components in question are provided. Also the permeability constant is an important factor that controls coupling between substrate and components.
The most commonly used material for building MEMS structures and devices is silicon, which is a material having a comparatively high dielectric constant.
However, most often the silicon is doped in order to increase conductivity and thus, the conductivity will contribute to negative effects, such as increased losses and non-linearity effects.
Stray capacitances are the most important negative factor in both RF applications and in capacitive measurements, and traditional silicon processing will inherently cause such problems.